Liquid crystal displays are widely used in personal computers, mobile equipment monitors and televisions since they have various advantages, e.g., in their low voltage and low consumption power and high possibility for reduction in size and profile. Although a variety of modes depending on how liquid crystalline molecules are aligned in a liquid crystal cell have been proposed for such liquid crystal displays, the dominating mode has hitherto been a TN mode in which liquid crystalline molecules are in an aligned state that their orientations twist by about 90° toward an upper side substrate from a lower side substrate.
In general a liquid crystal display is made up of a liquid crystal cell, an optical compensation film and a polarizer. The optical compensation film is used for dissolution of coloring of images and expansion of a viewing angle, and a stretched birefringent film or a transparent film coated with a liquid crystal is employed as the optical compensation film. For instance, Japanese Patent No. 2587398 discloses the art of expanding a viewing angle by applying to a TN-mode liquid crystal cell the optical compensation film formed by coating a discotic liquid crystal on a triacetyl cellulose film, forcing the liquid crystal into an aligned state and fixing the aligned state. However, liquid crystal displays for television use, which are supposed to be equipped with big screens and to be viewed from various angles, have stringent demands on viewing angle dependence, so even the foregoing art cannot satisfy such demands. Under these circumstances, liquid crystal displays employing modes different from the TN mode, such as an IPS (In-Plane Switching) mode, an OCB (Optically Compensatory Bend) mode and a VA (Vertically Aligned) mode, have been studied. The VA mode in particular has captured the spotlight in liquid crystal displays for TV uses because it can ensure high contrast and relatively high manufacturing yield.
In VA mode, however, although almost complete black display can be given in the normal direction for a panel, light leakage generates when the panel is viewed from an oblique direction, thus the viewing angle becoming narrow. In order to improve this, it has been proposed to reduce light leakage by disposing a retardation plate having such refractive index anisotropy that the refractive index in the film thickness direction is sufficiently smaller than the refractive index in the film plane in at least one position between a liquid crystal layer and a polarizing plate (for example, JP-A-62-210423). It has also been proposed to reduce light leakage by using in combination a first retardation plate having a positive uniaxial refractive index anisotropy and a second retardation plate having such negative refractive index anisotropy that the refractive index in the film thickness direction is sufficiently smaller than the refractive index in the film plane (for example, Japanese Patent No. 3027805). It has further been proposed to improve viewing angle characteristics of a VA mode liquid crystal display by using an optically biaxial retardation plate wherein refractive indexes in three-dimensional directions of the film are all different from each other (for example, Japanese Patent No. 3330574).
However, these methods reduce light leakage only for a light of a certain wavelength region (for example, green light around 550 nm) and do not take into consideration light leakage for a light of other wavelength region (for example, blue light around 450 nm and red light around 650 nm). Therefore, there remained so-called color shift that, when black display is viewed from an oblique direction, the display gives coloration to blue or red.